1. Field of the Invention
This invention is directed to a seeker system for a missile which utilizes a wafer scale phased array seeker operated in a multi-function mode to simultaneously guide a missile to its target while providing anti-radiation seeking and jamming of antimissile defense radars and antimissile guidance heads.
2. Background Information
Current radar guided missiles utilize a mechanically driven antenna to locate and track a target. Several modes of operation are used. In a missile which operates in the active radar mode, the missile transmits on board generated radar pulses and receives radiation reflected from the target to its mechanically driven antenna. Semiactive radar missiles, which are generally used in the air to air environment, track on reflected radiation propagated by a ground or airborne launch vehicle. If the target is a radar system, some missiles can operate in an anti-radiation mode in which they track on the RF energy radiated by the target radar. Often a target will direct a jamming signal at a radar guided missile in an attempt to saturate its receiver or deceive its tracking system. In such an environment, many missiles can switch to a home on jam mode in which they guide on the jamming beam.
In currently anticipated realistic combat scenarios, an incoming missile could encounter awesome countermeasures, particularly surrounding a high value target such a large ship. Such vessels are equipped with sophisticated and powerful self defense fire control systems which use shipboard radars and antimissile missiles to track and destroy incoming missile threats Antimissile missiles can also be launched from other vessels supporting the high value target. Large numbers of incoming missiles are needed to overwhelm these defenses at great cost.
The mechanically driven radar antennas of the current missiles have a narrow look angle and slew too slowly to track widely separated targets, search radars and jamming sources. Phased array seekers have been developed which are electronically agile. By controlling the relative phase of RF energy between multiple apertures in the array, the resulting beam can be rapidly slewed over a wide area, for instance, a 120 degree cone about the center line of the array. Unfortunately, conventional phased array seeker systems are too large for a cost efficient missile. However, U.S. Pat. No. 4,823,136 discloses a wafer scale phased array seeker system in which a plurality of transmit/receive cells are incorporated into a three inch (7.62 cm) or four inch (10.16 cm) diameter wafer of semiconductor material. The seeker is indicated for use as a radar transmitter/receiver with a narrow band antenna, and for use as an ECM transmitter/receiver with a broad band antenna.
U.S. Pat. No. 4,735,379 discloses a missile guidance system which utilizes an electronic scanning antenna. Several targets can be tracked simultaneously and the course of the missile controlled to maintain the plural targets within the range of action of the missile until a particular target is singled out using prelaunch stored target characteristics which are compared with the detected target returns. While this system has some capability of avoiding defensive jammers, it does not have the ability to jam defensive radar and antimissile weapons systems.
There remains a need for an affordable missile seeker system which can operate with a high P.sub.k (probability of kill) against a heavily defended target.
It is the object of the present invention to satisfy this need by providing a multi-mode missile seeker system which can track a target while providing self-defense ECM.
It is the further object of the invention to provide such a missile seeker system which can jam a threat which is widely separated angularly from the target being tracked.
It is another object of the invention to provide such a missile seeker system which can operate in either an active or semiactive radar mode or in an anti-radiation mode.
It is yet another object of the invention to provide such a missile seeker system which can jam an ECM source or home on a jamming target.
It is an additional object of the invention to provide a missile seeker system which can assess threats and automatically jam the greatest threats while continuing to track the target.
It is an overall object of the invention to achieve all of the above objectives with a missile seeker system which is of a size and weight such that it can be used in a practical sized missile.